This is a large (males to 30 cm, females to 43 cm) freshwater turtle with an elongated, oval carapace with straight or curved sides and a slightly serrated posterior rim. Longitudinal rugosities are usually present along the sides, and the sides may occasionally be restricted in the region of the 6th marginals. A medial keel is pronounced in young individuals, but in adults it is reduced and restricted to the posterior vertebrals or absent. Vertebral 1 is as long as broad or longer than broad, vertebrals 2-5 are broader than long. The carapace is green to olive or dark brown to black. A pattern of light markings varies from narrow transverse bands to wavy reticulations. The plastron lacks a hinge and has a posterior notch. The plastral formula is abd > an > fem >< pect >< gul >< hum. The plastron is yellow to light orange and frequently has a symmetrical, wavy, dark figure which generally follows and diffuses outward from the seams. Dark marks are also present on the undersides of the marginals and on the bridge. These markings can be absent, greatly reduced, or highly variable in some populations. The head is moderate in size with a slightly protruding snout. The upper jaw is either smooth or slightly notched with short cusps present in some populations. The skin is olive, brown or black with a variable number of longitudinal cream or yellow stripes. The supratemporal stripe is usually broad above and behind the tympanum. The neck, limbs and tail are also marked with yellow stripes. Old males may be partially melanistic, with the markings on the head, limbs and shell obscured by dark brown or black vermiculations.
The karyotype is 2n = 50: 26 macrochromosomes (16 metacentric, 6 submetacentric, and 4 telocentric) and 24 microchromosomes (Killebrew, 1977a).
Adult males have longer foreclaws than do females, and long thick tails with the vent beyond the carapacial rim. Females have shorter tails with the vent beneath the posterior marginals.
Pseudemys concinna ranges from Maryland south to northern peninsular Florida and throughout the central and southern United States north to Illinois, Missouri, and Kansas and west to eastern Texas and Oklahoma.
Presently only three subspecies are recognized (Seidel and Dreslik, 1996). The river cooter Pseudemys concinna concinna (LeConte, 1830) is found in piedmont streams from Maryland south to Georgia, west to eastern Texas, Oklahoma, Kansas, Missouri, and east through southern Illinois, southwestern Indiana, southern Kentucky, and Tennessee, and at several localities in western West Virginia. It has numerous (11+) head and neck stripes, a "C"-shaped mark is often present on the 2nd pleural, a dark plastral figure (which may fade in adults), and the cutting surface of the upper jaw irregular or slightly notched at the midline. Now included in this subspecies are the formerly recognized races P. c. hieroglyphica (Holbrook, 1836), P. c. mobilensis (Holbrook, 1838), P. floridana hoyi (Agassiz, 1857) and P. c. metteri Ward, 1984. Should the western populations prove in thefuture to be a valid subspecies, the name [l][m]Glossary[/m][r]hoyi[/r]hoyi Agassiz, 1857 has precedence over metteri Ward, 1984. The Florida or common cooter P. c. floridana (LeConte, 1830) lives in coastal plain streams from southeastern Virginia southward across northern Florida to Alabama. It has fewer than 11 head and neck stripes, one or more wavy transverse bars on the 2nd pleural, usually no dark markings on the plastron, and a rounded upper jaw with no medial notch. P. c. suwanniensis Carr, 1937a, the Suwannee River cooter, occupies an allopatric ranges in west central Florida. Its head and neck are blackish with light green or yellow lines, the 2nd pleural usually has a "C"-shaped light mark, the plastron has a dark figure. The male carapace often become almost totally black with age.
As the common name indicates, this species is an inhabitant of large rivers, but it may also be found in lakes, impoundments, marshes and canals within its range.
The smallest mature female P. c. suwanniensis recorded by Jackson (1970) was 14.0 cm in carapace length, the smallest male was 14.6 cm. In Alabama, male testes are largest in spring, decline in size during the summer, and begin to enlarge again in the fall (Thomas and Mount, 1973). Females have enlarged follicles in late winter, which are probably ovulated in late April or May. Ovarian activity declines during summer and early fall. The ovaries of several large females collected on 30 July in Louisiana revealed that by then the breeding season is over for most, but two had enlarged follicles that presumably could have been deposited later that year (Dundee and Rossman, 1989).
Mating usually occurs in the spring. The male pursues the female, sniffing at her tail, swims to a position dorsal to her, extends his neck and head outward and downward over hers, positions his elongated foreclaws just anterior and to the side of her snout, and vibrates them rapidly in front of her face. If properly stimulated, she will sink to the bottom and allow the male to mount her.
Nesting usually takes place in late May or June, but some clutches may be laid as late as mid-July to late summer. Common nest sites are open areas within 30 m of water with either sandy of friable loam soil. One or more smaller side nests which may hold 1-2 eggs, are often dug adjacent to the main nest chamber.
Clutches range from 9-29 eggs, although 19-20 eggs are probably more normal. The eggs are pinkish white, ellipsoidal (29.0-44.0 x 22.0-30.5 mm) with parchment-like shells bearing many fine nodules. Hatching probably takes in approximately 80-100 days, depending on the weather. Most hatchlings emerge in August or September, but those from more northern populations may be forced to overwinter in the nest.
Hatchlings have green shells and are more brightly marked than adults. The hatchling carapace is rounded and 27.0-36.5 mm long; a medial keel is present.
As in other species of Pseudemys, P. concinna is mostly a plant eater as an adult; young turtles are at first carnivorous but become more herbivorous with age. Plant foods include algae (Cladophora), and vascular plants (Ceratophyllum, Egeria, Sagittaria, Vallisneria); animals eaten are snails (Amnicola, Eimia, Hydrilla, Leptodictyum, Najas, Nassarius, Olivella), fish (Opsanus) (Lagueux et al., 1995; Bjorndal et al., 1997). Eighty to 100% of the P. c. suwanniensis in one Florida spring were found to have eaten Ceratophyllum and Egeria (Lagueux et al., 1995).
IUCN Red List Status (1996)